add -lrt for glibc < 2.17 compatibility

ChangeLog

@@ -1,3 +1,11 @@
+Tue Mar 21 13:51:04 CET 2017
+	Use "-lrt" to link libmicrohttpd if we are using
+	clock_gettime() as needed by glibc < 2.17. -CG
+
+Tue Mar 21 13:42:07 CET 2017
+	Allow chaining of suspend-resume calls withuot
+	the application processing data from the network. -CG
+
 Mon Mar 20 0:51:24 MSK 2017
 	Added autoconf module for detection whatever shutdown of listening socket
 	trigger select. This is only reliable method to use such feature as some

configure.ac

@@ -939,6 +939,8 @@ AC_LINK_IFELSE(
   ],
   [
     AC_DEFINE([HAVE_CLOCK_GET_TIME], [1], [Define to 1 if you have `clock_get_time', `host_get_clock_service' and `mach_port_deallocate' functions.])
+# For glibc < 2.17, we need -lrt:    
+    MHD_LIBDEPS="-lrt $MHD_LIBDEPS"
     AC_MSG_RESULT([[yes]])
   ],
   [AC_MSG_RESULT([[no]])